1. Field of the Invention
The present invention relates to a ceramic electronic component and a glass paste.
2. Description of the Related Art
Hitherto, ceramic electronic components such as ceramic capacitors have been used for electronic devices such as cellular phones and portable music players. Ceramic electronic components generally include a ceramic body having a surface at which an end portion of each of inner electrodes is exposed and outer electrodes disposed so as to cover a portion of the ceramic body in which the inner electrode is exposed. Examples of the outer electrodes include outer electrodes obtained by applying and baking a conductive paste to form a sintered metal film and plating the sintered metal film as disclosed in Japanese Unexamined Patent Application Publication No. 2002-203737 and outer electrodes formed only of a plating film as disclosed in Japanese Unexamined Patent Application Publication No. 2004-327983.
However, since the conductive paste used when such a sintered metal film is formed has high viscosity, the sintered metal film has a large thickness. For example, it is described in Japanese Unexamined Patent Application Publication No. 2002-203737 that first and second electrode layers (sintered metal films) have a thickness of about 50 μm to 90 μm.
When the outer electrodes are each formed of a sintered metal film, the baking temperature at which the conductive paste is baked is high. Therefore, the interdiffusion between a ceramic component contained in the ceramic body and a glass component in the conductive paste occurs and consequently a reaction layer may be formed at the interface between the ceramic body and the sintered metal film. A plating solution enters the ceramic body through a portion in which the reaction layer has been formed, which poses problems in that the mechanical strength of the ceramic body decreases and the moisture resistance degrades. Furthermore, an excessively high baking temperature poses a problem in that glass floating occurs through precipitation of a glass component on the surface of the sintered metal film and consequently a plating film is not easily formed on the surface of the sintered metal film.
Japanese Unexamined Patent Application Publication No. 2004-327983 proposes a method for forming an outer electrode using only a plating film. When the outer electrode is formed of only a plating film, the thickness of the outer electrode can be decreased compared with, for example, the case where an outer electrode is formed by baking a conductive paste.
Since a plating solution does not contain a glass component, the reaction layer is not formed at the interface between the ceramic body and the plating film. Therefore, problems such as a decrease in mechanical strength and a degradation of moisture resistance caused by formation of the reaction layer do not easily occur. Furthermore, a problem of glass floating and a problem in that a plating film is not easily formed do not occur.
However, when the outer electrode is formed of a plating film, the ceramic body needs to be directly immersed in a plating solution, which poses a problem in that the plating solution enters the ceramic body through an exposed portion of an inner electrode. As a result, the moisture resistance may degrade.
When the outer electrode is formed of only a plating film, the plating film and the ceramic body are not chemically bonded to each other, but only physically bonded to each other. This poses a problem in that the adhesiveness between the plating film and the ceramic body degrades. As a result, moisture or the like easily enters the ceramic body through a portion between the plating film and the ceramic body during the use of ceramic electronic components, which may degrade the moisture resistance.